Depending on whether a rotor or rotor carrier is disk-shaped or annular in cross section, gas turbine rotors having integral blading are known as blisks or blings. Disk-shaped gas turbine rotors having integral blading are described as blisks (bladed disks), and annular gas turbine rotors having integral blading are described as blings (bladed rings).
From the related art, it is known to manufacture gas turbine rotors having integral blading in a process described as milling from a solid blank. The process of milling from a solid blank is primarily used in the manufacture of relatively small gas tubine rotors. Thus, the process of milling from a solid blank is particularly suited for the series production of blisks or blings having relatively small titanium blades. It is problematic to mill blisks or blings from a nickel alloy due to the poor cutting properties of the material.
Another method known from the related art for manufacturing gas turbine rotors having integral blading provides for attaching prefabricated rotor blades to the rotor carrier or to the hub using a suitable joining process, for example so-called linear friction welding or so-called inductive pressure welding, or also diffusion welding. When manufacturing relatively large gas turbine rotors or gas turbine rotors having relatively large blades, the process of attaching prefabricated rotor blades to the rotor carrier is more economical and cost-effective than the process of milling from a solid blank.
In the last-mentioned method known from the related art for manufacturing gas turbine rotors having integral blading, prefabricated rotor blades are attached to the rotor carrier. These factory prepared rotor blades are, in particular, forged parts, which, with respect to their geometric design, especially their thickness, have already been adapted to the nominal shape of the rotor blades of the gas turbine rotor. This means that, under the related art methods, the finished rotor blades attached to the rotor carrier are, for the most part, already finish-machined. Under the related art, following the joining operation, it is merely necessary to finely machine, namely surface-machine the prefabricated rotor blades. Attaching substantially finish-machined rotor blades to the rotor carrier necessitates a costly adaptation between an attachment site for the blade root on the rotor carrier and the finished geometry of the rotor blade, in order to be able to compensate for positional deviations inherent in the joining process. This adaptation is very complex and thus increases the cost of manufacturing gas turbine rotors having integral blading. Moreover, the largely finish-machined rotor blades, which, under the related art methods, are attached to a rotor carrier, are components that typically must be purchased at a high cost from outside suppliers. This also makes it expensive to manufacture gas turbine rotors having integral blading.
Against this background, the object of the present invention is to devise a novel method for manufacturing gas turbine rotors having integral blading.
In accordance with an embodiment of the present invention, a method is provided for manufacturing a gas turbine rotor having integral blading, comprising the steps of producing unmachined rotor blade parts, joining at least one of the unmachined rotor blade parts to a rotor carrier, machining the unmachined rotor blade part(s) attached to the rotor carrier to a nominal shape of a rotor blade(s), and thereafter, finely machining the unmachined rotor blade part(s) to end contours of the gas turbine rotor having integral blading. In accordance with one variant of this embodiment the step of producing includes separating raw rotor blade parts out of a strip-shaped or band-shaped material of substantially uniform thickness and, thereafter, cambering and twisting said raw rotor blade parts to produce unmachined rotor blade parts, each of the unmachined rotor blade parts having a substantially uniform thickness and a desired three-dimensional twist. In accordance with another variant of this embodiment, the step of producing includes separating raw rotor blade parts out of an extruded profile of a substantially uniform thickness.